Overboost (from N54 Engine Tech Manual)

[ersatzS2]

Sorry if this observation has been made previously; I haven't seen it. I just read the N54 Tech manual in the sticky. Interesting to note that the stock setup allows for overboost of up to .8 bar, or 11.2 psi. That's a nice premium over the standard boost of 8lbs, and probably accounts for the variability of horsepower numbers being measured and reported, as well as the growing sense that HP is "under-reported" by BMW.

[turbomg]

Originally Posted by ersatzS2

allows for

What is "allows for"?

Does that mean something like "will wait until, before pulling timing to save warranty claims"?

FWIW, most tuners are aiming for about 15psi on the stock puny turbos.

[ersatzS2]

Originally Posted by turbomg

What is "allows for"?

Does that mean something like "will wait until, before pulling timing to save warranty claims"?

FWIW, most tuners are aiming for about 15psi on the stock puny turbos.

Meaning that: The engine ecu will allow boost to build to 11psi before the wastegate dumps when the engine is experiencing heavy loads. Like accelerating up a hill, or nailing it in high gear while going slowly.

HP ratings on turbo engines are highly elastic anyhow; they are much more dependent for example on air temp, both because cold air is denser (hence you are compressing more 02 per unit of volume) but also because the intercooler is so much more efficient.

My point was only that if the engine rating of 300hp is based on standard boost levels of 8psi, then seeing ~300 at the wheels as some are reporting isn't surprising if the ecu is allowing pressure spikes to 11psi.

Assuming the mfr built in sizeable safety margins, It also makes me feel aftermarket tuners who tune to 15psi are operating well within safe levels: basically just 4 psi over stock...